The goal for this renewal application is to gain in-(depth knowledge of PI3K and RAS-MAPK signaling and cooperating pathways governing pancreatic ductal adenocarcinoma (PDAC) to guide clinical trials with prominent drug development candidates and to identify new therapeutic points of attack in these pathways. The program project consists of a multiple-disciplinary team of basic and clinical investigators with a strong track record of working together and with complementary strengths in tumor biology, mouse genetics, cancer metabolism, PI3K signaling and functional genomics. The Program consists of 3 highly interactive projects (Project 1: DePinho. Hahn and Chin. DFCI;Project 2;Cantley. BIDMC and Bardeesy. MGH: Project 3: Jacks and Van der Heiden. MIT) with the integrating goals of determining the roles of KRAS* synthetic lethal genes in PDAC development and maintenance, the effect of co-extinction of PI3K/MEK pathways In PDAC and associated drug resistance mechanisms, the Impact of MEK/PI3K inhibition on PDAC metabolism, and the effect of inhibiting glutamine metabolism on PDAC. Project 1 will employ whole genome RNAi and bioinformatics analyses to identify and validate druggable co extinction targets that synergize with MEKi or Pi3Ki in suppressing KRAS* PDACs. In addition, context specific gain of function in vivo genetic screens will be performed to identify additional druggable targets underlying acquired resistance or playing cooperative roles with Pl3K/MEK signaling. Project 2 will address the central hypothesis that KRAS*-driven PDAC utilizes the PI3K and MAPK pathways in a redundant way to drive tumor growth and that a critical role for these pathways involves the maintenance of tumor metabolism. Project 2 will determine the impact of MEKi/PlSKi on PDAC cell signaling, metabolism, and therapeutic response. These efforts will be coupled with an investigation of metabolic biomarkers for MEK/Pl3K signaling and identification of mechanisms of therapeutic resistance which would be critical in guiding future therapeutic trials in this area. Project 3 will investigate the importance of a series of potential therapeutic targets in tumor maintenance by developing both conditional RNAi systems for use in cell culture and transplant models as well as sophisticated genetically-engineered mouse models designed to allow conditional deletion of genes in autochthonous tumors. These Projects will be enabled by highly innovative cores for Molecular Imaging (Weissleder, MGH). Experimental Pathology (Loda/Chu. DFCl), Biobank (Thaver, MGH). and Mouse Engineering (DePinho/Homer, DFCI): and assisted by an administrative core to provide scientific and fiscal oversight (DePinho, DFCl).